Microcatheters, including neuromicrocatheters, are generally microtubes inserted into the body through a blood vessel such as the femoral artery and have a variety of uses (see, e.g., U.S. Pat. Nos. 6,306,124 and 6,454,738). Microcatheters have a distal and a proximal end where, typically, at or near the very distal end, a marker band is employed to permit the clinician to visualize the microcatheter positioning during in vivo use. The marker band typically comprises a metal or metal alloy ring such as platinum, nitinol and/or gold rings which can be visualized via fluoroscopy.
Microcatheters are typically used to embolize the neurovasculature such as in treating arteriovenous malformations (AVMs), aneurysms, and the like in a relatively non-invasive manner. See, for example, Jones, et al., (U.S. Pat. No. 5,843,050), which discloses a microcatheter for negotiating small tortuous vessels or the neurovasculature.
A variety of microcatheters, suitable for the wide variety of applications, are available commercially. Neurovascular embolization devices include intravascular compositions which solidify in vivo so as to permanently occlude blood flow to cerebral aneurysms and cerebral arteriovenous malformations. Suitable intravascular compositions include, by way of example only, cyanoacrylates which polymerize in vivo to form a solid mass as well as solutions of a biocompatible, water insoluble polymer dissolved in a non-aqueous solvent such as dimethyl sulfoxide (“DMSO”) whereupon introduction into the vasculature, the DMSO dissipates and the polymer precipitates in the aqueous based blood composition. Such intravascular compositions further comprise a contrast agent to assist in visualization of the formed mass.
One problem associated with microcatheter use particularly in effecting neurovascular embolization is the phenomena referred to as “reflux.” Typically, during neurovascular embolization, a solid mass is formed from an embolic agent, such as for example an embolic liquid, delivered in situ to the embolization site. The embolic agent, in the form of a prepolymer such as a cyanoacrylate prepolymer or a polymeric solution such as an Onyx® formulation (available from ev3 Neurovascular, Irvine, Calif. and comprises ethylene vinyl alcohol copolymer, DMSO and tantalum) is ejected distally from the microcatheter tip and forms a solid mass at this distal point. However, in certain cases, “flow back” or “reflux” of the liquid composition prior to solidification can occur and the embolic agent can engulf the microcatheter tip. In such cases, the microcatheter tip can be entrapped in the solid mass upon solidification of the embolic agent. Even in instances where reflux is avoided, the microcatheter may become trapped in the blood vessel as a result of vasospasm causes by the presence of DMSO or other spasmodic materials in the embolic composition.
When reflux or vasospasm occurs, the clinician is often reluctant to use excessive force to remove the neuromicrocatheter for concerns over vessel tear or rupture. Typically, the clinician either must attempt to withdraw the neuromicrocatheter by force, often resulting in microcatheter breakage, or must cut the microcatheter. In either event, a portion of the neuromicrocatheter remains in the patient's vasculature. Alternatively, the clinician can attempt to minimize reflux by underfilling the cavity thereby leaving less than a desirable therapeutic outcome and yet not completely eliminating the risk of a trapped neuromicrocatheter.